Midwest Levee Inspectors, a joint venture between Intuition & Logic and Hultgren-Tillis Engineering, was contracted by the United States Army Corps of Engineers (USACE) Omaha District to evaluate the Cottonwood Springs Dam Conduit.



In order to restore the reliability of the system to operate as intended during a flooding event the team was required to evaluate the existing conduit, then identify and develop methods of rehabilitating the conduit. The conduit has experienced significant settlement following construction of the dam that caused cracking and leakage of the joints below the apex of the embankment as well as axial and transverse cracking throughout the length of the conduit.



The field evaluation consisted of inspections, sampling and testing precipitate leachate and monolith cores, and detailed LiDAR survey of the monolith interior.  The inspections were performed by a four person team consisting of a dam specialist, a geotechincal engineer, a structural engineer and a hydraulic engineer.  The inspection team prepared conduit damage maps documenting the number, location and type of cracking, deterioration, precipitate and previous repair patching and epoxy injections. The inspection was followed up by an evaluation analysis based on the data gathered in the field.  The evaluation included a hydraulic capacity analysis; a cavitation analysis and structural analysis.  The team also evaluated several repair alternatives, including: no action; steel lining; HOBAS pipe lining; chemical grouting of the in situ soil; resin injection of joints; and three types of cast in place pipe.